Table of Contents
Silica fume is a by-product from the production of elemental silicon or alloys containing silicon in electric arc furnaces. At a temperature of approximately 2000°C the reduction of high-purity quartz to silicon produces silicon dioxide vapor, which oxidizes and condenses at low temperatures to produce silica fume.
Where do we get silica fume?
Production. Silica fume is a byproduct in the carbothermic reduction of high-purity quartz with carbonaceous materials like coal, coke, wood-chips, in electric arc furnaces in the production of silicon and ferrosilicon alloys.
What is silica fume admixture?
Silica fume is a mineral admixture, composed of submicron particles (100 to 150 times smaller than a grain of cement) of amorphous silicon dioxide. Silica fume powder is gray to off-white in color, and is available in several product forms and packaging options.
Why do we add silica fume in concrete?
Condensed silica fume is a very fine, amorphous, and reactive mineral admixture. It reacts readily with the calcium hydroxide, which is produced during Portland cement hydration. Silica addition refines pore structure and produces concrete of improved mechanical strength.
Which industry produces silica fume?
Silica fume (SF) is a by-product of the smelting process (reduction of high-purity quartz with coal in electric furnaces) in the production of silicon and ferrosilicon alloys.
How much does silica fume cost?
Condensed silica fume costs from $400-$1,000/ton, which is significantly higher than portland cement ($90/ton).
What is silica fume and its uses?
Silica fume, a by-product of the ferrosilicon industry, is a highly pozzolanic material that is used to enhance mechanical and durability properties of concrete. It may be added directly to concrete as an individual ingredient or in a blend of portland cement and silica fume.
What is the difference between silica fume and microsilica?
Silica fume consists primarily of amorphous (non-crystalline) silicon dioxide(SiO2). Concrete containing silica fume can have very high strength and can be very durable. Micro Silica Fume or Microsilica is finer particle than Cement. It is produced by some chemical processing of the ash.
What are the properties of silica fume?
Various properties of silica fume cocnrete, including slump, air-content, compressive strength, flexural strength, permeability, and permeable void volume were investigated, and the effect of the silica fume replacement ratio of cement is described.
Is silica fume toxic?
Repeated exposure can damage the eyes. * High exposure to Silica, Amorphous (Fume) can cause a flu-like illness with headache, fever, chills, aches, chest tightness and cough. * Repeated exposure to Silica, Amorphous (Fume) can cause lung damage (fibrosis).
How do you mix silica fume in concrete?
(1) Put in aggregate, then put in silica fume, cement and dry mix, then add water and other additives. (2) Put in coarse aggregate + 75% water + silica fume + 50% fine aggregate, stir for 15-30 seconds, then put in cement + concrete admixture + 50% fine aggregate + 25% water, and stir until uniform.
How does silica fume react to concrete?
Pozzolanic reaction occurs between silica fume and the CH, producing additional CSH in many of the voids around hydrated cement particles. Because of the high surface area of silica fume particles affecting the mobility of water within concrete, segregation and bleeding of concrete are virtually eliminated.
What are the disadvantages of high silica cement?
disadvantages of silica fume in concrete Silica fume concrete is too viscous and difficult to apply.it is not easy to wipe the surface. Silica fume requires a high amount of water and needs to be used with a superplasticizer. The price of silica fume is relatively high compared to cement and fly ash.
What is the difference between fly ash and silica fume?
Silica Fume is typically much more reactive, particularly at early ages , because of its higher silicon dioxide content and because of its very small particle size. Disadvantages of Fly Ash: – High-carbon fly ash materials tend to use more water and darken the concrete as well.
Is silica fume a pozzolan?
Silica fume (SF) Condensed silica fume has been classified as a pozzolan by the American Concrete Institute (ACI) Committee 226 on cementitious materials [22].
What is Ggbs material?
GGBS (Ground Granulated Blast-furnace Slag) is a cementitious material whose main use is in concrete and is a by-product from the blast-furnaces used to make iron. The iron ore is reduced to iron and the remaining materials form a slag that floats on top of the iron.
What is metakaolin powder?
Metakaolin is a dehydroxylated form of the clay mineral kaolinite. Metakaolin is commonly used in the production of ceramics, but is also used as cement replacement in concrete. Metakaolin has a smaller particle size (∼1–2 μm) and higher surface area compared with portland cement, but a larger particle size than SF.
Is silica a cement?
Many common construction materials contain silica including, for example, asphalt, brick, cement, concrete, drywall, grout, mortar, stone, sand, and tile.
What is the meaning of pozzolanic?
: finely divided siliceous or siliceous and aluminous material that reacts chemically with slaked lime at ordinary temperature and in the presence of moisture to form a strong slow-hardening cement.
Which is not pozzolanic material?
Which of the following is not a pozzolanic material? Explanation: Pozzolans are silicate based materials that form cementitious materials. Fly ash, silica fumes and slag are composed of oxide of silicon. Cinder is a coal residue.
Why the silica fume is known as Super pozzolan?
Because of its chemical and physical properties, it is a very reactive pozzolan. Concrete containing silica fume can have very high strength and can be very durable. Because of its fine particles, large surface area, and the high SiO2 content, silica fume is a very reactive pozzolan when used in concrete.
Is silica a silicon dioxide?
Silicon dioxide (SiO2), also known as silica, is a natural compound made of two of the earth’s most abundant materials: silicon (Si) and oxygen (O2). Silicon dioxide is most often recognized in the form of quartz. It makes up more than 95 percent of known rocks on the planet.
Is code for silica fume?
Basic Details IS Number : IS 15388 : 2003 Language : English ICS Code : ICS 91.100.15 Product Id : 15388 Scope : Download.
Is silica a carcinogen?
Silica, Crystalline (Respirable Size). NTP classification: Known to be a human carcinogen. International Agency for Research on Cancer (IARC) Monographs on the Evaluation of Carcinogenic Risks for Humans.
Is silica safe to eat?
According to the United States Department of Labor, about 2.3 million people in the U.S. are exposed to silica at work. As long as you aren’t inhaling silica in its crystalline form, it appears to be safe to consume at the levels set out by the FDA.
What is the lung disease caused by silica dust?
Silicosis is a long-term lung disease caused by inhaling large amounts of crystalline silica dust, usually over many years. Silica is a substance naturally found in certain types of stone, rock, sand and clay.
What is the fly ash concrete?
Fly ash use in concrete improves the workability of plastic concrete, and the strength and durability of hardened concrete. Fly ash use is also cost effective. When fly ash is added to concrete, the amount of portland cement may be reduced. Benefits to Fresh Concrete.
What is the percentage of silica in cement?
The cement contains 35 to 40 percent lime, 40 to 50 percent alumina, up to 15 percent iron oxides, and preferably not more than about 6 percent silica.
Where do we get silica fume?
Production. Silica fume is a byproduct in the carbothermic reduction of high-purity quartz with carbonaceous materials like coal, coke, wood-chips, in electric arc furnaces in the production of silicon and ferrosilicon alloys.
What is silica fume admixture?
Silica fume is a mineral admixture, composed of submicron particles (100 to 150 times smaller than a grain of cement) of amorphous silicon dioxide. Silica fume powder is gray to off-white in color, and is available in several product forms and packaging options.
Why do we add silica fume in concrete?
Condensed silica fume is a very fine, amorphous, and reactive mineral admixture. It reacts readily with the calcium hydroxide, which is produced during Portland cement hydration. Silica addition refines pore structure and produces concrete of improved mechanical strength.
Which industry produces silica fume?
Silica fume (SF) is a by-product of the smelting process (reduction of high-purity quartz with coal in electric furnaces) in the production of silicon and ferrosilicon alloys.
How much does silica fume cost?
Condensed silica fume costs from $400-$1,000/ton, which is significantly higher than portland cement ($90/ton).
What is silica fume and its uses?
Silica fume, a by-product of the ferrosilicon industry, is a highly pozzolanic material that is used to enhance mechanical and durability properties of concrete. It may be added directly to concrete as an individual ingredient or in a blend of portland cement and silica fume.
How do you mix silica fume in concrete?
(1) Put in aggregate, then put in silica fume, cement and dry mix, then add water and other additives. (2) Put in coarse aggregate + 75% water + silica fume + 50% fine aggregate, stir for 15-30 seconds, then put in cement + concrete admixture + 50% fine aggregate + 25% water, and stir until uniform.
What is the difference between silica fume and microsilica?
Silica fume consists primarily of amorphous (non-crystalline) silicon dioxide(SiO2). Concrete containing silica fume can have very high strength and can be very durable. Micro Silica Fume or Microsilica is finer particle than Cement. It is produced by some chemical processing of the ash.
How does silica fume react to concrete?
Pozzolanic reaction occurs between silica fume and the CH, producing additional CSH in many of the voids around hydrated cement particles. Because of the high surface area of silica fume particles affecting the mobility of water within concrete, segregation and bleeding of concrete are virtually eliminated.
What is in fly ash?
Fly Ash, a very fine, powdery material composed mostly of silica made from the burning of finely ground coal in a boiler. Bottom Ash, a coarse, angular ash particle that is too large to be carried up into the smoke stacks so it forms in the bottom of the coal furnace.
What is metakaolin powder?
Metakaolin is a dehydroxylated form of the clay mineral kaolinite. Metakaolin is commonly used in the production of ceramics, but is also used as cement replacement in concrete. Metakaolin has a smaller particle size (∼1–2 μm) and higher surface area compared with portland cement, but a larger particle size than SF.
Why is silica fume a good pozzolan?
Silica fume is a pozzolanic material composed of extremely fine, amorphous spheres produced as a byproduct in the manufacture of silicon metals. It has a high water demand and it is more reactive than natural pozzolan or fly ash. It increases the compressive strength significantly.
Is silica fume toxic?
Repeated exposure can damage the eyes. * High exposure to Silica, Amorphous (Fume) can cause a flu-like illness with headache, fever, chills, aches, chest tightness and cough. * Repeated exposure to Silica, Amorphous (Fume) can cause lung damage (fibrosis).
What are the disadvantages of high silica cement?
disadvantages of silica fume in concrete Silica fume concrete is too viscous and difficult to apply.it is not easy to wipe the surface. Silica fume requires a high amount of water and needs to be used with a superplasticizer. The price of silica fume is relatively high compared to cement and fly ash.
Does silica increase strength?
Silica fume has been successfully used to produce very high-strength, low-permeability, and chemically resistant concrete. Addition of silica fume by itself, with other factors being constant, increases the concrete strength.
What are the properties of silica fume?
Various properties of silica fume cocnrete, including slump, air-content, compressive strength, flexural strength, permeability, and permeable void volume were investigated, and the effect of the silica fume replacement ratio of cement is described.
Does silica fume improve workability?
Silica fume is known to improve the mechanical characteristics of concrete. It is observed that the optimum dose of silica fume is 5% (by weight), when used as part replacement of OPC. The silica fume inclusion increases the workability and strength of concrete considerably.
What is the difference between metakaolin and kaolin?
As nouns the difference between metakaolin and kaolin is that metakaolin is a dehydroxylated form of the clay mineral kaolinite while kaolin is a fine clay, rich in kaolinite, used in ceramics, paper-making, etc.
What is the meaning of pozzolanic?
: finely divided siliceous or siliceous and aluminous material that reacts chemically with slaked lime at ordinary temperature and in the presence of moisture to form a strong slow-hardening cement.
Why is Metakaolin used in concrete?
Metakaolin is a pozzolan, probably the most effective pozzolanic material for use in concrete. This results in improvements to resistance of the hardened concrete to attack by sulfates, chloride ions and other aggressive substances, such as mineral and organic acids.
Is silica a carcinogen?
Silica, Crystalline (Respirable Size). NTP classification: Known to be a human carcinogen. International Agency for Research on Cancer (IARC) Monographs on the Evaluation of Carcinogenic Risks for Humans.
Is silica safe to eat?
According to the United States Department of Labor, about 2.3 million people in the U.S. are exposed to silica at work. As long as you aren’t inhaling silica in its crystalline form, it appears to be safe to consume at the levels set out by the FDA.
What is the lung disease caused by silica dust?
Silicosis is a long-term lung disease caused by inhaling large amounts of crystalline silica dust, usually over many years. Silica is a substance naturally found in certain types of stone, rock, sand and clay.
